Effect of a single dose of dexamethasone on serum concentrations of thyroid hormones

The bidirectional relationship of thyroid disease and atrial fibrillation: Established knowledge and future considerations

Atrial fibrillation (AF) tends to occur frequently in patients with thyroid disease, primarily hyperthyroidism. In hyperthyroidism, increased levels of thyroid hormones, via intra- and extranuclear mechanisms, have profound effects on cardiac electrophysiology. Hypothyroidism carries a lower risk for AF and is mainly associated with the overtreatment of hypothyroid patients. New-onset AF is frequently the only manifestation of thyroid disease, which renders screening for thyroid dysfunction in that scenario clinically useful. Managing thyroid disease and comorbid AF is essential. This includes thyroid hormones control along with conventional AF therapy. However, there are several open issues with this comorbid duo. The optimal management of thyroid disease and its impact on AF burden remains obscure. There is scanty information on clear-cut benefits for therapy of subclinical thyroid disease and screening of asymptomatic patients. Furthermore, the immunogenetic overlap between the autoantibodies in Graves' disease and AF genesis may lead to novel therapeutic implications. The objective of this review is to summarize the up-to-date epidemiology, pathogenesis, pathophysiology and management of interacting thyroid disease and AF.

Thyroid and COVID-19: a review on pathophysiological, clinical and organizational aspects

BACKGROUND

Thyroid dysfunction has been observed in patients with COVID-19, and endocrinologists are requested to understand this clinical issue. Pandemic-related restrictions and reorganization of healthcare services may affect thyroid disease management.

OBJECTIVE AND METHODS

To analyze and discuss the relationship between COVID-19 and thyroid diseases from several perspectives. PubMed/MEDLINE, Google Scholar, Scopus, ClinicalTrial.gov were searched for this purpose by using free text words and medical subject headings as follows: "sars cov 2", "covid 19", "subacute thyroiditis", "atypical thyroiditis", "chronic thyroiditis", "hashimoto's thyroiditis", "graves' disease", "thyroid nodule", "differentiated thyroid cancer", "medullary thyroid cancer", "methimazole", "levothyroxine", "multikinase inhibitor", "remdesivir", "tocilizumab". Data were collected, analyzed, and discussed to answer the following clinical questions: "What evidence suggests that COVID-19 may induce detrimental consequences on thyroid function?"; "Could previous or concomitant thyroid diseases deteriorate the prognosis of COVID-19 once the infection has occurred?"; "Could medical management of thyroid diseases influence the clinical course of COVID-19?"; "Does medical management of COVID-19 interfere with thyroid function?"; "Are there defined strategies to better manage endocrine diseases despite restrictive measures and in-hospital and ambulatory activities reorganizations?".

RESULTS

SARS-CoV-2 may induce thyroid dysfunction that is usually reversible, including subclinical and atypical thyroiditis. Patients with baseline thyroid diseases are not at higher risk of contracting or transmitting SARS-CoV-2, and baseline thyroid dysfunction does not foster a worse progression of COVID-19. However, it is unclear whether low levels of free triiodothyronine, observed in seriously ill patients with COVID-19, may worsen the disease's clinical progression and, consequently, if triiodothyronine supplementation could be a tool for reducing this burden. Glucocorticoids and heparin may affect thyroid hormone secretion and measurement, respectively, leading to possible misdiagnosis of thyroid dysfunction in severe cases of COVID-19. High-risk thyroid nodules require a fine-needle aspiration without relevant delay, whereas other non-urgent diagnostic procedures and therapeutic interventions should be postponed.

DISCUSSION

Currently, we know that SARS-CoV-2 could lead to short-term and reversible thyroid dysfunction, but thyroid diseases seem not to affect the progression of COVID-19. Adequate management of patients with thyroid diseases remains essential during the pandemic, but it could be compromised because of healthcare service restrictions. Endocrine care centers should continuously recognize and classify priority cases for in-person visits and therapeutic procedures. Telemedicine may be a useful tool for managing patients not requiring in-person visits.

Triiodothyronine and cortisol levels in the face of energetic challenges from reproduction, thermoregulation and food intake in female macaques

Energy availability drives an individual's fitness and can be affected by diverse energetic challenges. The assessment of hormones involved in metabolic activity and energy mobilization provides a gateway to the study of physiological adaptations in response to changes in energy availability. Here, we investigated immunoreactive urinary total triiodothyronine (uTT3, thyroid hormone secreted through the hypothalamus-pituitary-thyroid axis and regulating the basal metabolic rate) alongside glucocorticoids (i.e. urinary cortisol, uCort, secreted through the hypothalamus-pituitary-adrenal axis and mediating energy mobilization) in wild female Assamese macaques (Macaca assamensis). Combining more than 2900; of behavioral data from 42 adult females with physiological data from 382 urine samples, we evaluated both uTT3 and uCort in relation to potential energetic challenges encountered by a female, namely fluctuations in energy intake, travel distance, reproductive state and minimum ambient temperature. As predicted, levels of both hormones changed in response to variation in energy intake with a tendency toward a positive effect on uTT3 and a significant negative effect on uCort levels. Unexpectedly, neither hormone was influenced by variation in travel distance. Reproductive state affected both hormones with higher levels of uTT3 and uCort in the second half of gestation. Finally, a decrease of minimum temperature triggered an increase in uCort but unexpectedly not in uTT3. Collectively, our results highlight the respective contribution of two endocrine axes when facing energetic challenges and the underlying metabolic strategies to cope with them. Overall, assessing thyroid hormones together with glucocorticoids provides an integrative picture in the evaluation of an individual's energy status.

Applications for non-invasive thyroid hormone measurements in mammalian ecology, growth, and maintenance

Thyroid hormones (THs) play a pivotal role in the regulation of metabolic activity throughout all life stages. Cross-talk with other hormone systems permits THs to coordinate metabolic changes as well as modifications in growth and maintenance in response to changing environmental conditions. The scope of this review is to explain the relevant basics of TH endocrinology, highlight pertinent topics that have been investigated so far, and offer guidance on measuring THs in non-invasively collected matrices. The first part of the review provides an overview of TH biochemistry, which is necessary to understand and interpret the findings of existing studies and to apply non-invasive TH monitoring. The second part focuses on the role of THs in mammalian ecology, and the third part highlights the role of THs in growth and maintenance. The fourth part deals with the advantages and difficulties of measuring THs in non-invasively collected samples. This review concludes with a summary that considers future directions in the study of THs.

Influence of maternal thyroid hormones during gestation on fetal brain development

Thyroid hormones (THs) play an obligatory role in many fundamental processes underlying brain development and maturation. The developing embryo/fetus is dependent on maternal supply of TH. The fetal thyroid gland does not commence TH synthesis until mid gestation, and the adverse consequences of severe maternal TH deficiency on offspring neurodevelopment are well established. Recent evidence suggests that even more moderate forms of maternal thyroid dysfunction, particularly during early gestation, may have a long-lasting influence on child cognitive development and risk of neurodevelopmental disorders. Moreover, these observed alterations appear to be largely irreversible after birth. It is, therefore, important to gain a better understanding of the role of maternal thyroid dysfunction on offspring neurodevelopment in terms of the nature, magnitude, time-specificity, and context-specificity of its effects. With respect to the issue of context specificity, it is possible that maternal stress and stress-related biological processes during pregnancy may modulate maternal thyroid function. The possibility of an interaction between the thyroid and stress systems in the context of fetal brain development has, however, not been addressed to date. We begin this review with a brief overview of TH biology during pregnancy and a summary of the literature on its effect on the developing brain. Next, we consider and discuss whether and how processes related to maternal stress and stress biology may interact with and modify the effects of maternal thyroid function on offspring brain development. We synthesize several research areas and identify important knowledge gaps that may warrant further study. The scientific and public health relevance of this review relates to achieving a better understanding of the timing, mechanisms and contexts of thyroid programing of brain development, with implications for early identification of risk, primary prevention and intervention.

Thyrotoxic hypercalcemia treated with corticosteroids

A 42-year-old man presenting with symptomatic hypercalcemia was successfully treated with corticosteroids. Initially he was thought to suffer from Addison's disease. A thyrotoxic state was, however, disclosed during the treatment. Evidence suggests that the hypercalcemia was caused by thyrotoxicosis. The effects of thyroid and adrenocortical hormones on calcium metabolism are discussed. Corticosteroids seem valuable in differentiating thyrotoxic hypercalcemia from coincidental hyperparathyroidism.

The influence of endogenous cortisol on the peripheral conversion of thyroxine in patients with acute myocardial infarction

A study was performed to elucidate whether endogenous cortisol, as previously suggested, could be responsible for the decreased T3 levels seen in euthyroid patients with acute myocardial infarction. Levels of these hormones as well as levels of T4 and reverse-T3 were monitored in 31 consecutive patients admitted to the Coronary Care Unit with symptoms of precordial pain or with acute arrhythmias. Sixteen of the patients had proven myocardial infarction, the remaining 15 were used as a control group. The results demonstrated that a reduction of T3 levels was seen in the infarction group without evidence of a statistically significant difference between the daily mean cortisol levels. No significant difference could be observed in T4 or reverse-T3 levels in the two groups or in T3 levels in the control group. It is concluded that the decrease in T3 levels is not a consequence of the increased levels of endogenous cortisol.

The role of endogenous cortisol in patients with non-thyroidal illness and decreased T3 levels

The aim of the study was to elucidate if endogenous cortisol, as previously suggested, could be involved in the mechanism behind the reduced serum T3 levels seen in euthyroid patients with various non-thyroidal illnesses. The correlation between the serum levels of T3 and cortisol was investigated in 41 hospitalized patients with non-thyroidal illness during hyperpyrexia. The results showed a correlation coefficient of -0.94, indicating a close reciprocal association between the two hormones. Cortisol may thus be one factor associated with the decreased T3 levels seen in euthyroid patients with non-thyroidal illness. The results also indicate a close parallelism between the total and free T3 levels during hyperpyrexia.

Early hormonal therapy stabilizes hemodynamics during donor procurement

BACKGROUND

Hemodynamic instability has been implicated in the loss of otherwise transplantable organs. We examined the hypothesis that administration of hormonal therapy early during donor management would stabilize hemodynamics and increase the number of organs procured.

METHODS

We retrospectively analyzed 133 consecutive donor records from a single organ procurement organization. Controls (C) received no early hormonal therapy. A steroid group (S) received methylprednisolone only and a combination hormonal therapy group (CH) received thyroxine, methylprednisolone, dextrose, and insulin at the start of donor management (t(0h)). Adrenergic support was adjusted to maintain mean arterial blood pressure (MAP) at > or =60 mm Hg. Doses of adrenergic agents were assessed at t(0h), 4 hours (t(4h)), and just prior to procurement (t(proc)).

RESULTS

Baseline characteristics were similar in all groups. Dosages of adrenergic agents decreased over time in all groups. A significant decrease in adrenergic requirements was seen in the CH group compared with the C group at t(4h) and t(proc). A trend toward decreased adrenergic requirements was noted in S compared with C at t(4h) and t(proc). Slightly more total organs were procured from S and CH compared with C.

CONCLUSIONS

Significantly less adrenergic support was required with early use of CH. A similar (although nonsignificant) reduction was seen with S. The benefit(s) of CH vs corticosteroids alone remains uncertain and requires further study.

Thyroid function in children with Cushing's disease before and after transsphenoidal surgery

The degree of thyroid impairment and the effects on growth have not been investigated in children with Cushing's disease. We followed the thyroid function of 24 children and adolescents (12 males and 12 females) with CD (age, 12.9 +/- 3.2 years; mean +/- SD), who were successfully treated by transsphenoidal surgery. Patients were evaluated before, and 3, 6, and 12 months after TSS. Analysis of variance and linear correlation were performed between thyroid function tests and body weight and mass index and bone age. Preoperative free thyroxine levels (1.37 +/- 0.03 ng/dl) were significantly higher than those at 3 months (1.17 +/- 0.05 ng/dl, p < 0.05), but similar to those at 6 and 12 months postoperatively. Preoperative T3 (114.2 +/- 7.7 ng/dl) and TSH (1.36 +/- 0.2 IU/ml) were significantly lower than the postoperative values at 3 (158.9 +/- 6.8 and 2.3 +/- 0.3, respectively), 6 (159.1 +/- 10.8 and 2.5 +/- 0.3, respectively), and 12 months (136 +/- 6.5 and 2.2 +/- 0.3, respectively) (all p < 0.05). One patient had frank hypothyroidism (fT4 < 1 ng/dl) before surgery. Five additional patients had secondary hypothyroidism in the immediate postsurgical period; two of them had normal thyroid function 2 and 3 years postoperatively. One patient has remained hypothyroid for more than 5 years since surgery. No significant correlation was found between thyroid function and body weight, BMI, or BA. We conclude that hypothyroidism was an infrequent complication of CD and TSS. Mild suppression of thyroid function occurs in most children and adolescents with CD before and in the first few months after TSS, but it fully resolves after 6 months and does not correlate with the growth delay and obesity of these patients.

Thyrotropin levels during hydrocortisone infusions that mimic fasting-induced cortisol elevations: a clinical research center study

Both short term fasting and administration of high doses of glucocorticoids lead to marked suppression of serum TSH levels in healthy subjects. However, it is not known whether the more mild serum cortisol elevations seen during fasting can account for fasting-induced TSH suppression. To study this question, eight healthy subjects each underwent three 2-day studies: 1) baseline (adlibitum diet), 2) fasting (56 h of total caloric deprivation), 3) hydrocortisone (HC) infusions at a dose and pulsatile pattern that reproduced cortisol levels measured during each subject's fasting study. Subjects required 34-46 mg HC/24 h to achieve these cortisol levels. During each study, blood samples were drawn every 15 min during the final 24 h for serum cortisol and TSH levels. A TRH stimulation test was performed at the end of each study. By design, fasting and HC infusions induced similar mild increases in 24-h serum cortisol levels (32% over baseline), with the most significant increases seen between 1400-0200 h. Fasting decreased 24-h mean and pulsatile TSH levels 65% from baseline, whereas HC infusions decreased mean and pulsatile TSH levels 51% from baseline. Daytime (0800-0200 h) TSH levels were identical in the two studies, whereas nocturnal (0200-0800 h) TSH levels during HC infusions fell midway between baseline and fasting studies. Serum total T3 and TSH responses to TRH were decreased to a similar degree by fasting or HC infusions. These results suggest that mild elevations in endogenous cortisol levels may mediate at least in part fasting-induced changes in TSH secretion and thyroid hormone levels. In addition, these data show that near-physiological doses of HC and resulting changes in serum cortisol levels within the normal range can cause significant decreases in serum TSH levels.

Alterations in the pituitary-thyroid and pituitary-adrenal axes--consequences of long-term mifepristone treatment

The effects of short-term administration of the antiprogestin and antiglucocorticoid, mifepristone, have been well characterized. However, little is known about the effects of prolonged administration of mifepristone. We analyzed hormonal parameters in four female and three male patients with unresectable meningioma who were treated with mifepristone (200 mg/d) for 20 to 40 months. Serum samples were collected at monthly intervals approximately 24 hours following mifepristone ingestion. Serum thyrotropin (TSH), thyroxine (T4), free T4 (fT4), 3,5,3-triiodothyronine (T3), prolactin, and cortisol were analyzed by fluoroimmunoassay, and androstenedione by radioimmunoassay (RIA). Levels of mifepristone and its three most proximal metabolites were measured by high-performance liquid chromatography. TSH values increased significantly (P < .005, one-way ANOVA), with the most pronounced increase evident during the first 3 months of mifepristone treatment. Despite these changes, concentrations of TSH remained within the normal range throughout the treatment period. There were no significant changes in serum T4, fT4, T3 or prolactin; however, a transient decrease in serum T4 was noted at 2 to 3 months. Cortisol and androstenedione values increased significantly and in parallel (P < .05), suggesting an adrenal origin also for androstenedione. As during short-term administration, levels of mifepristone and its metabolites remained stable in the micromolar range. Individual levels of mifepristone were significantly correlated with those of TSH and cortisol. This suggests that the alterations in the pituitary-thyroid and -adrenal axes occurred in a concentration-dependent manner. It is concluded that long-term mifepristone treatment results in resetting of the pituitary-thyroid balance. As in the case with cortisol and androstenedione, it is likely that the alterations in serum TSH are due to the antiglucocorticoid properties of mifepristone. The clinical significance of these biochemical alterations in thyroid homeostasis remains to be determined. However, monitoring thyroid function during long-term mifepristone treatment appears to be warranted.

Thyrotropin-releasing hormone gene expression in the human hypothalamus

We studied the distribution of mRNA coding for thyrotropin-releasing hormone (TRH) in the human hypothalamus by means of in situ hybridization. In 10% formalin-fixed paraffin-embedded tissue sections of five hypothalami, TRH mRNA-containing cells were found in several nuclei and areas. Numerous TRH mRNA-containing cells were detected in the medial region of the caudal part of the paraventricular nucleus. These neurons were heavily labeled and mainly small to medium-sized. Few, lightly- and medium-labeled, small cells were detected in the suprachiasmatic nucleus. In addition, heavily labeled single cells were found in the perifornical area and the anterior- and lateral hypothalamic regions. In the latter region, occasional heavily labeled cells were found just dorsal to the supraoptic nucleus. Neither in the supraoptic nucleus nor in the sexually dimorphic nucleus of the preoptic area were TRH mRNA-containing cells found. This is the first description of TRH mRNA containing cells in the human hypothalamus.

T4 uptake into the perfused rat liver and liver T4 uptake in humans are inhibited by fructose

Recently, we described a two-pool model for 3,5,3'-triiodothyronine uptake and metabolism in the isolated perfused rat liver. Here, we applied this model to investigate transmembrane thyroxine (T4) transport and its possible ATP dependence in vivo. These studies are performed in perfused rat livers during perfusion with or without fructose in the medium, as it has been shown that intracellular ATP is decreased after fructose loading. Furthermore, we studied serum T4 tracer disappearance curves in four human subjects before and after intravenous fructose loading. In the perfused rat liver, we found a decrease in liver ATP concentration and a decrease in medium T4 disappearance and T4 uptake in the liver pool after fructose. Furthermore, it was shown that, when corrected for differences in the medium free hormone concentration, only transport to the metabolizing liver pool was decreased after fructose perfusion, whereas uptake in the nonmetabolizing pool was unaffected. Disposal, corrected for differences in transport into the metabolizing pool, was also not affected after fructose. In the human studies, intravenous fructose administration induced a rise in serum lactic acid and uric acid, indicating a decrease in liver ATP. This was observed concomitant with a decrease in serum tracer T4 disappearance during the first 3 h after fructose administration. These results suggest ATP dependence of transport of iodothyronines into the liver in vivo and show that, in the rat liver and in humans, uptake of T4 may be regulated by intracellular energy stores; in this way the tissue uptake process may affect intracellular metabolism and bioavailability of thyroid hormone.

Severity of alcoholic liver disease and markers of thyroid and steroid status

Alcoholic liver disease is associated with abnormalities in circulating levels of thyroid, adrenal and gonadal steroid hormones. The relative importance of ethanol consumption and severity of liver disease in the aetiology of these changes and their relationship to clinical abnormalities are unclear. We studied 31 subjects with alcohol-induced liver disease divided into three groups according to the severity of histological features: fatty change, hepatitis and cirrhosis. Circulating concentrations of thyroid, adrenal and gonadal steroid hormones, together with their major binding proteins, were measured in all subjects, and changes related to histology and tests of liver function, as well as clinical endocrine status. A reduction in circulating free tri-iodothyronine (fT3) was seen in subjects with alcoholic hepatitis and cirrhosis, in association with normal or reduced levels of thyrotrophin (TSH). The absence of abnormalities in subjects with fatty change despite similar ethanol intake to the other groups, and correlations between fT3 and liver function tests, suggest that changes in fT3 reflect the severity of underlying liver disease. Similarly, marked increases in circulating cortisol in the hepatitis and cirrhosis groups, and correlations between cortisol and liver function, suggest that changes largely reflect hepatic disease. The absence of clinical features of hypothyroidism or Cushing's syndrome in these groups, despite abnormalities of fT3 and cortisol, suggest an altered tissue sensitivity to hormone effects. In contrast, increases in circulating oestradiol and reductions in testosterone were found in all three groups in males. These findings suggest that both direct effects of ethanol and hepatic dysfunction determine changes in gonadal steroids in males.

Glucagon-induced changes in plasma thyroid hormone concentrations in healthy dogs resemble "euthyroid sick syndrome"

We recently demonstrated that glucagon infusion induced a decline in T3 and a rise in rT3 in anesthetized dogs. These changes in T3 and rT3 may be attributed, at least in part, to anesthesia itself, since general anesthesia is known to cause lowering of T3 and an elevation in rT3 during the perioperative period. Therefore, to eliminate the contribution, if any, of anesthesia to these changes in T3 and rT3, we assessed plasma glucose, T3 resin uptake (T3RU), T4, free T4, T3 and rT3 concentrations following intravenous glucagon (0.5 mg) or normal saline (0.5 ml) administration at frequent intervals for 3 h in 6 conscious dogs fasted for 16 h. No significant alterations were noted in T4, free T4, and T3RU levels during either study. However, glucagon infusion alone induced a significant fall in T3 (0.33 +/- 0.06 in nmol/l vs -0.03 +/- 0.03 nmol/l with normal saline; p less than 0.01) and marked elevations in glucose (3.66 +/- 0.22 mmol/l vs 0.61 +/- 0.11 nmol/l with normal saline, p less than 0.001) and rT3 concentrations (0.11 +/- 0.02 nmol/l vs 0.005 nmol/l; p less than 0.001). Furthermore, the integrated responses of T3 and rT3 as assessed by cumulative changes and areas under the curves were markedly greater during glucagon infusion when compared with saline administration (p less than 0.01 for all comparisons). Since the elevations in levels of stress hormones known to ensue during anesthesia do not occur during a conscious resting state, we believe that hyperglucagonemia may be a major contributor of thyroid hormone alterations observed in several euthyroid sick states, not associated with stress, and may enhance these changes during euthyroid sick syndrome associated with stressful crises. Finally, these changes may be attributed to altered metabolism of iodothyronines in peripheral tissues as reflected by lowered T3/T4 and increased rT3/T4 ratios.

TSH secretion in Cushing's syndrome: relation to glucocorticoid excess, diabetes, goitre, and the 'sick euthyroid syndrome'

Thyrotrophin (TSH) secretion was studied in 63 patients with Cushing's syndrome (53 patients with pituitary dependent Cushing's disease, eight with adrenocortical tumours, and two with the ectopic ACTH syndrome). Prior to treatment, TSH response to 200 micrograms of TRH intravenously was significantly decreased compared to controls; TSH response was 'flat' (increment less than 2 mU/l) in 34 patients (54%). Patients with a flat response to TRH had significantly higher morning and midnight cortisol levels than patients with a TSH response of 2 mU/l and more; this was not due to differences in serum thyroid hormone levels. Basal TSH, TSH increment after TRH, and stimulated TSH value, but not serum triiodothyronine, were correlated with cortisol measurements (0800 h serum cortisol, midnight cortisol, and urinary free corticoid excretion). After exclusion of 40 patients with additional disease (severe systemic disease, diabetes mellitus, or goitre), cortisol-TSH correlations were even more pronounced (r = -0.73 for midnight cortisol and stimulated TSH levels), while in the patients with additional complications, these correlations were slight or absent. Successful treatment in 20 patients was associated with a rise in thyroid hormone levels and the TSH response to TRH. These results indicate that (1) the corticoid excess but not serum T3 is the principal factor regulating TSH secretion in Cushing's syndrome, (2) a totally flat response to TRH is rare, and (3) TSH suppression and lower than normal serum thyroid hormone levels are reversible after treatment. Since factors like severe systemic disease, diabetes mellitus and goitre also affect TSH secretion, they tend to obscure the statistically significant correlations between cortisol excess and TSH secretion.

Suppressive effects of dexamethasone on hypothalamic-pituitary-thyroid axis function in depressed patients

This study investigated the effects of dexamethasone (1 mg orally) on the function of the hypothalamic-pituitary-thyroid (HPT) axis. We determined pre- and post-dexamethasone thyroid-secreting hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), reverse T3 and cortisol levels in 61 depressed inpatients. Dexamethasone had a pronounced suppressive effect on basal TSH and FT3 levels. It had a significant stimulating effect on rT3 levels. No differences were found between melancholic and minor depressives in the effects of dexamethasone on basal TSH, FT3 and rT3. Cortisol non-suppressors were characterized by less suppression of basal TSH values.

Exacerbation of autoimmune thyroid dysfunction after unilateral adrenalectomy in patients with Cushing's syndrome due to an adrenocortical adenoma

Little is known about the factors that cause exacerbations of autoimmune thyroid dysfunction. One possibility is an alteration in adrenocortical function, since glucocorticoids are known to alter both pituitary-thyroid and immunologic function. We encountered three patients in whom overt autoimmune thyroid disease developed after unilateral adrenalectomy for Cushing's syndrome due to an adrenocortical adenoma. We compared the postoperative changes in thyroid function in these patients with those in 21 other patients with Cushing's syndrome who underwent the same treatment. After unilateral adrenalectomy, one of the three patients had transient hyperthyroidism and a low thyroid uptake of 131I, indicative of silent thyroiditis. After the same surgical procedure, the second patient had hypothyroidism, where-as the third patient had transient hyperthyroidism at first, and hypothyroidism then gradually developed. All three patients had serum antithyroid antibodies, the titers of which increased after surgery. In the remaining 21 patients (only 2 of whom had antithyroid antibodies initially), the serum concentrations of thyroxine, triiodothyronine, and thyroxine-binding globulin and the secretion of thyroid-stimulating hormone increased after surgery from values that were low or near the lower limit of normal to values still well within the normal range. None of these patients had clinically evident thyroid disease or increased antithyroid-antibody titers. We conclude that reductions in the secretion of glucocorticoid may exacerbate subclinical autoimmune thyroid disease. Patients with Cushing's syndrome due to adrenocortical adenoma who have thyroid antibodies should be followed closely after treatment, because thyroid dysfunction may develop.

Thyrotropic activity of the ovine corticotropin-releasing factor in the chick embryo

An injection of several doses of ovine corticotropin-releasing factor (oCRF) was made into an allantoic blood vessel of 18-day-old chick embryos. All doses used (0.5, 1, 2, and 5 micrograms) induce a quick increase of plasma corticosterone concentrations after 15 and 30 min and 1 and 2 hr and this in a dose-dependent manner with the high doses having a prolonged effect lasting up to 2 hr. An increase in plasma levels of thyroxine (T4) and triiodothyronine (T3) was observed after 1 and 2 hr. After the oCRF injection, no stimulation of the hepatic 5'-monodeiodination activity was observed and there was no increase, but even a small decrease in the T3 to T4 ratio could be calculated. It was therefore concluded that oCRF in the chick embryo has a thyrotropic effect presumably by stimulating the release of thyrotropin from the pituitary.

Triiodothyronine, thyroxine, and TSH response to dexamethasone in depressed patients and normal controls

In view of recent investigations concerning alterations of thyroid function in depression, the pre- and postdexamethasone levels of T3, T4, and TSH of 14 patients during depression and after recovery were studied, in addition to those of 27 healthy controls. A reduction of T3 and TSH levels was shown to be dependent on the depressive state, with a tendency to lower T4 levels after recovery. Dexamethasone had a pronounced suppressive effect on TSH levels in healthy controls and in patients after recovery, but not during the depressive episode. These results point to an inadequate suppressibility of the hypothalamo-pituitary-thyroid (HPT) axis to dexamethasone during depression. There are close interrelations between the hypothalamo-pituitary-adrenal (HPA) and the HPT axes that are possibly affected during depressive illness.

Three-compartmental analysis of effects of D-propranolol on thyroid hormone kinetics

Tracer thyroxine (T4), 3.3',5-triiodothyronine (T3), and 3,3',5'-triiodothyronine (rT3) kinetic studies were performed in normal T4 substituted subjects before and during oral D-propranolol treatment to determine whether changes in thyroid hormone metabolism in a propranolol-induced low-T3 syndrome result from inhibition of 5'-deiodination or inhibition of transport of iodothyronines into tissues. Data were analyzed according to a three-compartmental model of distribution and metabolism. T4 plasma appearance rate decreased by 16% (P less than 0.01), reflecting a decreased intestinal absorption of orally administered T4 during propranolol. Serum T4 and free T4 levels increased significantly by 14%, whereas T4 metabolic clearance rate (MCR) was lowered by 26% (P less than 0.001). No changes were observed in size of the three T4 compartments or in fractional and mass transfer rates of T4 from plasma to the rapidly (REP) and slowly (SEP) equilibrating pools. Serum T3, free T3, T3 plasma pool, T3 mass transfer rate to REP and SEP, and the T3 pool masses were all significantly decreased during propranolol to a similar extent as the T3 plasma production rate (PR). T3 MCR decreased by 14% (P less than 0.05). Serum total and free rT3 increased, whereas the rT3 MCR was substantially lowered during propranolol (P less than 0.001). The rT3 plasma pool, rT3 REP and SEP, and the mass transfer rates to REP and SEP increased, whereas no alterations were observed in rT3 PR and fractional transfer rates of rT3 to REP and SEP.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of increased circulating corticosterone on serum and thyroidal concentrations of iodothyronines and the responses to thyrotrophin in the immature fowl (Gallus domesticus)

Four-week-old fowl were given subcutaneous implants containing a mixture of corticosterone: cholesterol (1:4, w/w) to raise serum corticosterone concentration. The effects on circulating thyroxine (T4), triiodothyronine (T3), and reverse T3 (rT3), thyroidal T3 and T4 and responses to thyrotrophin (TSH) were examined. Increased circulating corticosterone caused an increase in the plasma concentration of T4 and a decrease in T3 and rT3 indicating reduced extrathyroidal 5 and 5' monodeiodination of T4. After single injections of 0.1 IU TSH/kg body weight were given 3 and 13 days after corticosterone implants there was an increase in the T3 response and a delay and reduction in the T4 response. This may have been due to a corticosterone-induced increase in the synthesis of T3 relative to that of T4. Although the relative increase in thyroidal T3 concentration was greater 3 days after corticosterone implants were given, no significant shift in the T4:T3 ratio in the thyroid glands was observed.

Prevention of the eye closure defect in lgMl/lgMl fetal mice by thyroxine

The open-eye birth defect of mice caused by the lgMl mutation was prevented by prenatal administration of thyroxine (T4) to the pregnant mother. Treatment on days 10 to 11 of gestation was most effective in preventing open-eyes. A contrasting worsening of the defect was seen after treatment on day 14 of gestation. A dose-response relationship for prevention appeared to be present up to a dose of 0.1 mg/mouse, after which 39% of fetuses had both eyes closed compared to 2% in controls. Higher doses appeared to give little or no further increase in beneficial effect. Scanning electron microscopy was used to compare thyroxine-treated and untreated lgMl/lgMl and normal CBA/J day 16 or 17 fetal eyes. Mutant eye closure after thyroxine differed from untreated mutant in the growth of both upper and lower eyelids across the eye and in increased numbers of rounded periderm cells on the advancing lid edges. The underlying epithelial tissue layer appeared to fuse closed. The induced eye closure in the mutant was not normal, however. The periderm cell layer had disorderly fusion at the outer canthus, premature flattening, and failure to fuse in the inner canthus.

Propylthiouracil, ipodate, dexamethasone and periods of fasting induce different variations in serum rT3 in dogs

Fasting or administration of propylthiouracil (PTU), ipodate, or dexamethasone are all known to induce a pattern of low serum triiodothyronine (T3) concentrations and high serum reverse T3 (rT3) concentrations in humans. In the present study it was found that this is not a universal phenomenon. In normal dogs exposed to fasting or these various pharmacologic agents, the serum T3 level was always depressed as in humans. However, different variations in serum rT3 levels were observed. Fasting and PTU administration were accompanied by slight decreases in the serum rT3 concentration. A single dose of ipodate did not alter serum rT3 levels, but serum thyroxine (T4) levels increased by more than 50%. Dexamethasone induced a considerable increase in serum rT3 levels, while serum T4 levels were unaltered. The results suggest that the high serum rT3 level nearly always seen in "the low T3 syndrome" in humans is merely a coincidental character of the human species, and that it has little importance for in vivo homeostasis.

Endogenous cortisol and thyroid hormone levels in patients with acute myocardial infarction

Thyroid hormones and cortisol levels were serially measured over seven mornings and evenings in 23 consecutive patients with acute myocardial infarction (AMI) or acute coronary insufficiency (ACI). The patients were divided into two groups, high level cortisol (HLC) and low level cortisol (LLC) groups, according to mean morning and evening cortisol levels. The transient increase in plasma rT3, decrease in T3 and TSH was significantly greater in the HLC group. A diurnal variation in cortisol levels was observed in the LLC group 48 h and in the HLC group 72 h after admission. Taking the 23 patients together, no significant correlation was observed between infarct size (peak CPK levels) and the altered rT3, T4 or TSH levels. However, a significant correlation was obtained between the maximal change in T3, rT3 or TSH and the mean cortisol levels preceding these alterations, as well as between cortisol levels and infarct size. It is suggested that cortisol rather than infarct size may be the dominant factor involved in the alteration of thyroidal levels in AMI patients.

Prealbumin as a biochemical marker of nutritional adequacy in premature infants

To determine whether serum prealbumin would be useful in identifying adequacy of protein and calorie intake in premature infants, 17 infants between 26 and 33 weeks gestational age were studied throughout hospitalization. Serial anthropometric measurements, nutritional intake, and serum prealbumin concentrations were correlated. When mean intake of calories and protein was lower than 100 kcal/kg/day and less than 2 gm/kg/day, respectively, there was a significant difference in mean prealbumin values, compared with those in infants with a higher intake (P much less than 0.001). For infants with birth weights of 1000 gm or less, prealbumin correlated with protein intake (r = 0.66) and calorie intake (r = 0.64). In these infants, when protein intake exceeded 2 gm/kg/day, prealbumin concentrations increased to values reported for full-term infants in the first months of life. There was no significant correlation between intake of calories or protein and prealbumin values for infants born weighing greater than 1000 gm. Anthropometric measurements did not correlate with protein or calorie intake. We conclude that prealbumin is a sensitive measure of protein and calorie intake in premature infants, and that the definition of adequate nutrition may be different for premature infants of different birth weights and at various postconceptional ages.

Clinical and hormonal characteristics in women with anovulation and insulin-treated diabetes mellitus

Clinical characteristics and basal hormonal parameters related to ovulatory function were investigated in 22 diabetic patients with anovulation (group 1) and in nine normally menstruating diabetic patients (group 2) and 45 nondiabetic patients with anovulation (group 3). No significant differences according to control of the diabetes were demonstrated within the two diabetic groups. Groups 1 and 3 did not differ according to classification of anovulation. Group 1 had significantly (P less than 0.01) lower levels of prolactin (PRL), 17 beta-estradiol (E2), thyrotropin (TSH), 3,3',5-triiodothyronine (T3), and thyroxine (T4) than those of group 3, and significantly (P less than 0.01) lower levels of E2 and TSH than those of group 2. The urinary excretion of cortisol was significantly higher in group 1 than in group 2 (P less than 0.05) and group 3 (P less than 0.01). These data suggest a derangement in pituitary-gonadal feedback mechanisms or a depression of pituitary function in anovulatory diabetic patients, and we hypothesize that an increased central/peripheral dopamine and/or cortisol activity in these patients may to some extent influence the hypothalamic-pituitary axis.

Anterior pituitary, thyroid, parathyroid and adrenal responses to subtotal thyroidectomy in patients with Graves' disease

Changes in the serum levels of anterior pituitary, thyroid, parathyroid, and adrenal hormones following subtotal thyroidectomy in 31 patients with Graves' disease were investigated. In 14 patients, rapid ACTH tests were performed on the preoperative and the first, third, and seventh post-operative days. Remarkable differences were not seen with regard to the changes in anterior pituitary hormones or cortisol, compared to those seen during general surgery. As to the thyroid hormones, the serum level of triiodothyronine (T3) decreased markedly after surgery and fell to half that of the preoperative value on the first postoperative day. Thereafter, a low value of T3 was maintained during the early postoperative period. Unlike T3, the serum level of thyroxine (T4) decreased gradually until the 7th post-operative day. The levels of both epinephrine and norepinephrine increased transiently during surgery, but the serum level of norepinephrine increased again on the third postoperative day. In the postoperative period, almost half the number of patients showed an inadequate cortisol response to rapid ACTH tests. It is suggested that the unique responses, such as the rise in serum norepinephrine or an inadequate response of cortisol to ACTH, or hypocalcemia, after subtotal thyroidectomy in patients with Graves' disease is largely due to the rapid decrease of T3 in the hypothyroid state, as was noted during the postoperative period.

Pharmacological interference with in vitro tests of thyroid function

Numerous drugs may cause changes in the serum concentrations of T4 and of T3. If such alterations are not recognized an incorrect diagnosis may result. In moderate degrees of hypo- and hyperthyroidism thyroid hormone levels may be spuriously normal, or the influence of pharmacological substances may lead to false diagnosis of thyroid disease in euthyroid patients. Since prediction of such alterations remains uncertain, it may be necessary to perform additional investigations when a potential artefact is recognized. On the other hand many pharmacological agents, especially those which interact with neurotransmitters, may influence TSH secretion, too. The TRH-test may show an increase or decreased TSH response, although complete suppression is only rarely seen during high-dose glucocorticoid treatment when low TRH doses are applied. Because of TRH-test gives such wide separation between different clinical states false interpretations are generally less likely than with drug-induced changes in T4 and T3 values.

Occult thyrotoxicosis: a correctable cause of "idiopathic" atrial fibrillation

Serum total thyroxine, triiodothyronine and thyrotropin response to thyrotropin-releasing hormone were measured in 75 consecutive patients presenting to a cardiology clinic with atrial fibrillation with no obvious cardiovascular cause. A lack of response of serum thyrotropin to thyrotropin-releasing hormone, indicative of thyrotoxicosis, was found in 10 patients (13 percent), not all whom had raised serum thyroid hormone levels. These 10 patients were predominantly male, had no clinical signs of thyrotoxicosis and a relative excess of nonpalpable autonomous thyroid nodules demonstrated with scintigraphy. Eight of the 10 patients had reversion to stable sinus rhythm after treatment with iodine-131 or carbimazole, either spontaneously or after direct current cardioversion. It would appear that clinically occult thyrotoxicosis can be identified consistently only with the thyrotropin-releasing hormone test and is the cause of "idiopathic" atrial fibrillation in a significant proportion of patients.

Serum concentrations of thyrotropin, thyroid hormones and thyroid hormone-binding proteins during acute and recovery stages of idiopathic respiratory distress syndrome

A total number of 27 premature infants with idiopathic respiratory distress syndrome (IRDS) and 52 healthy controls with comparable gestational age and body weights were studied during the first month of life. In infants with IRDS a reduced thyrotropin (TSH) response to birth was suggested, as serum TSH was lower in IRDS patients than in controls during the first two days of life. Low serum concentrations of thyroid hormones were found in the acute stage of IRDS reaching minimal values by day 3--5. After that period an increase in thyroid hormone levels occurred. The serum T2 increased to the level of healthy prematures by day 6--10, whereas the serum T4 increased to normal levels by day 21--30. Serum concentrations of thyroxine-binding globulin (TBG) were significantly lower in IRDS patients than in healthy controls; a gradual increase to normal levels occurred during recovery. Serum prealbumin (TBPA) levels in IRDS infants increased rapidly after birth and exceeded levels of healthy infants. Serum albumin values were not significantly different in the two groups of infants. The serum T4/TBG ratios were low during recovery from IRDS.

Thyrotropin, free and total triiodothyronine, and thyroxine in serum during surgery

Changes in free and total thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) in serum were measured before, during, and for nine days after uncomplicated abdominal surgery in eight patients. The results showed a pronounced fall in total as well as in free T3 levels, amounting to 50% in both variables on the first postoperative day, and returning towards preoperative levels on the seventh and ninth day. Apart from an increase during surgery, free T4 levels were constant in the whole period despite a slight postoperative decrease in total T4. The TSH level fell about 80% within the first 24 postoperative h, but returned to the preoperative level thereafter. These results suggest a suppression of both T3 and TSH production during the pre- and early postoperative period.

No inhibition by Li+ of thyroxine monodeiodination to 3,5,3'-triiodothyronine and 3,3',5'-triiodothyronine (reverse triiodothyronine)

The possibility that lithium affects the conversion of thyroxine to 3,5,3"-triiodothyronine and 3,3',5'-triiodothyronine (reverse triiodothyronine) was studied by measurement of the serum concentractions of these parameters in five patients during the first week of lithium therapy. In three patients there was a decrease in serum thyroxine concentration and a slightly less pronounced decrease in that of serum 3,5,3'-triiodothyronine. In two patients, who also received L-tryptophan or flupentixol, no change was noted in the concentrations of these compounds. There was no increase in serum 3,3',5'-triiodothyronine concentration in any of the patients. No systematic change was found in the serum concentrations of thyrotropin or unsaturated thyroid-hormone binding proteins. The results obtained do not support the contention that lithium should inhibit the monodeiodenation of thyroxine to its active and inactive metabolites.

Rapid decrease in plasma-triiodothyronine during surgery and epidural analgesia independent of afferent neurogenic stimuli and of cortisol

Changes in circulating triiodothyronine (T3), thyroxine (T4), binding of thyroid hormones to plasma proteins (resin-T3 test), cortisol, and glucose were evaluated in sixteen patients undergoing abdominal hysterectomy. In eight of the patients afferent neurogenic impulses from the surgical area were blocked during and after operation by epidural analgesia. These patients were pain-free, and the normal stress-induced increase in cortisol and glucose was abolished. During epidural analgesia and general anesthesia plasma-T3 fell rapidly and values in the hypothyroid range were found 6 hours after skin incision. Similarly, an increase in the resin-T3 test reflected decreased binding of T3 to plasma proteins. Plasma-T4 decreased slightly during surgery and epidural analgesia (as it does when other anaesthetics are given), but increased during general anaesthesia. These results indicated that the alterations in thyroid hormones and their binding to plasma proteins after surgery are not caused by a stress-induced increase in plasma-cortisol or by neurogenic afferent stimuli from the surgical area, factors which are both known to affect concentrations of other hormones.

Measurement of serum 3,3',5'-(reverse) T3, with comments on its derivation

A radioimmunoassay for the measurement of l-3,3',5'-triiodothyronine (reverse TO, rT3) has been developed for use with unextracted serum. The highly specific antiserum showed no cross-reactivity with l-3,3'5-triiodothyronine (T3) or tetradiodothyroacetic acid (T4A) and cross-reaction with L-thyroxine (T4) was low enough to be discounted for routine assay purposes. If a normal amount of rT3 was added to serum T4 cross-reactivity decreased considerably. Serial dilutions of hyperthyroid sera gave dose-response curves which were parallel to the rT3 standard curve. Serum concentrations of rT3 (mean+/- SEM) were 0-68 +/- 0-02 nmo1/1 in sixty-seven normal subjects, 0-19 +/- 0-02 nmo1/1 in twelve hypothyroid patients and 1-18 +/- 0-12 nmo1/1 in seventeen hyperthyroid patients. In sixteen patients with TO-toxicosis rTO was 0-42 +/- 0-04 nmo1/1 and eighteen patients with high circulating TBG had a mean rT3 of 0-54 +/- 0-03 nmo1/1.